Many industries utilize an articulated vehicle with prime mover or tractor unit for transporting people, items or materials. Such vehicles typically include a heavy-duty towing unit that serves as a prime mover, providing motive power for hauling a series of trailing carts or carriages. The towing unit pulls the articulated carriages in the manner of a locomotive hauled railway train. The towing unit may be powered by an internal combustion engine, electric motor or hybrid. The towing unit is typically steered through the front wheels by a steering wheel operated by a human driver, and powered by its rear single or double axle. The towed carriages are then steered through drawbar couplings between the carriages. Some carriages may have steerable front wheels, while others may have steerable front and rear wheels.
A problem with such articulated vehicles is tracking, stability and control. Only the drawbar transmits forces to the carriage to indirectly cause the carriage to steer. The drawbar is not linked to the wheel movement components of a carriage. Consequently, the carriages tend to deviate from the path of the towing unit. Additionally, the carriages do not respond well to sharp turns of the towing unit. Furthermore, steering by essentially dragging a carriage through turns accelerates tire wear.
Another problem with such articulated vehicles is that the carriages do not provide any motive power. The carriages are pulled. Their wheels provide no torque. This compromises performance (e.g., traction and acceleration) on uneven terrain, when moving heavy loads, and on slick surfaces, such as in inclement weather.
What is needed is an articulated vehicle with carriages having wheels that steer to follow the path of the vehicle ahead, and optionally, differentials supplying torque to each wheel.
The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.